Phenoxyethanol is a common ingredient used to preserve cosmetic and pharmaceutical formulations for topical administration. Phenoxyethanol, sometimes known as 2-phenoxy-1-ethanol or ethylene glycol monophenyl ether, is a preservative used to provide biocidal activity against various microorganisms. Unfortunately, phenoxyethanol is also an irritant to the skin (see, for example, Lee E et al., Contact Dermatitis. 2007 March:56(3):131-6.). Similarly, benzyl alcohol is also known to induce skin irritation in vivo (Bagley, D. M. et al. (1996) Toxicol In Vitro 10(1): 1-6).
TRPV-1 (transient receptor potential vanilloid, subfamily V, receptor 1) is a protein encoded by the TRPV-1 gene. TRPV-1 is a non-selective, ligand-gated cation channel that is activated in response to increased temperature and mechanical or chemical stimulus. This receptor is found in the central nervous system as well as in non-neuronal cells, such as keratinocytes. Activation of TRPV-1 allows the transient flux of cations, especially Ca2+, into the cell. This Ca2+ influx stimulates the sensation of pain and has been associated with the onset of various cellular events such as inflammation. Activation of TRPV-1 is known to induce the release of pro-inflammatory mediators in human keratinocytes (Southall, M. D. et al. (2003) “J Pharmacol Exp Ther 304(1): 217-222).
TRPV-1 is known to be activated by capsaicin, a compound found in in chili peppers, and capsazepine is reported to be a TRPV-1 antagonist (Bevan, S. et al., Br J Pharmacol 107(2): 544-552). Other compounds known to be TRPV-1 antagonists are (E)-3-(4-t-butylphenyl)-N-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)acrylamide (Gavva, N. R. et al. (2005) J Pharmacol Exp Ther 313(1): 474-484), commercially available as AMG9810 from Tocris Bioscience, Bristol, United Kingdom, and 4-tertiary butyl cyclohexane (Kueper, T. et al. (2010) Exp Dermatol 19(11): 980-986), commercially available as SYMSITIVE 1609 from Symrise GmbH of Holzminden, Germany.
Applicants have now discovered that certain aromatic alcohols including phenoxyethanol activate TRPV-1. This is surprising in that applicants have also found that not all skin irritants activate TRPV-1 and not all topical anti-inflammatory compounds or analgesics inhibit the activation of TRPV-1. Thus, the discovery of the association between aromatic alcohols, their irritating properties, and TRPV-1 is unexpected.
Low irritation, aromatic alcohol-containing topical compositions are provided herein. Advantageously, they also do not require the presence of parabens (esters of para-hydroxybenzoic acid), the effects of which many consumers are concerned about. Further provided are methods of use thereof.